Cells were treated with pyrotinib for 24 h. (A) Representative picture of colony formation assay in TE-1 cells. (B) Percent of colony formation of pyrotinib treated TE-1 cells. (C) Representative picture of colony formation assay in KYSE30 cells. (D) Percent of colony formation of pyrotinib treated KYSE30 cells. **P < 0.01; ***P < 0.001 compared with control group.